RECENT WORK IN AGRICULTURAL SCIENCE. 



CHEMISTRY. 



Method for preparing strictly tenth-normal, fifth-normal, etc., hydro- 

 chloric or nitric acid, R. K. Meade (Jour. Amer. Chem. Soc, 23 (1901), No. 5, pp. 

 343-347). — The method described depends upon the decomposition of copper sulphate 

 in sohition 1)y the electric current. Barium chlorid is afterwards added to the solu- 

 tion, a double decomposition taking place, barium sulphate and hydrochloric acid 

 being formed. The process is carried out as follows: In making tenth-normal hydro- 

 chloric acid there is introduced into 12.487 gm. of crystallized copper sulphate in 

 500 cc. of water, a cylinder of copper foil attached to the negative wire and a i>lati- 

 num rod attached to the positive wire of an electric circuit with a current of from 

 1 to I5 amperes. The Ijeaker is covered with a watch-glass perforated for the rod, 

 and the current passed tlirough the solution for from 6 to 8 hours, or longer. After 

 removing and rinsing the apparatus, 12.215 gm. of crystallized barium chlorid, dis- 

 solved in water, is added and the solution made up to 1 liter. In order to have the 

 volume correct 26 cc. of water is added to fill the space taken up l>y the precipitate. 

 After the precipitate has settled the clear li(]uid is siphoned through a dry tube upon 

 a dry filter and caught in a dry stock-bottle. 



In making tenth-normal nitric acid by this method, 13.076 gm. of 1)arium nitrate 

 should be used in lieu of barium chlorid, the quantity of copper sulphate remaining 

 the same. Where the standard hydrochloric acid is for use with alkaline earths, it is 

 necessarj' to add a little in excess of the amount stated of barium chlorid. The 

 author prepared only tenth-normal and fifth-normal acids by this method, but states 

 that normal acid ran also proba1)ly be prepared, but that the waste caused by the 

 loss f>f solution retained in the jjrecipitate would be somewhat greater. 



The determination of nitrates in water containing chlorids, R. Marcille 

 [Ami. Ayrnn., .J7 (1901), No. 1-2, ]ip. 59'i-i'>00). — Tlie method proposed is a modifica- 

 tion of that of Grandval and Lajoux,' which is based ujjon the coloration produced 

 by the formation of trinitrophenol or picric acid when water containing nitrates is 

 treated with sulphophenic acid. The chlorids are eliminated by precipitation with 

 a i»ncentrated aminoniacal solution of silver sulphate, the determination of nitrates 

 being made in the solution without filtering to remove the precipitate. The method 

 of procedure is as follows: To 10 cc. of the water in a small porcelain dish add a few 

 drops more than enough of the silver solution to precipitate tlie chlorids; evaporate 

 to dryness at a temperature not much over 120° C. ; cool, add 1.5 to 2 cc. of sulpho- 

 phenic acid (8.1 parts of phenol to 100 partsof sulphuric acid), and mix toahomoge- 

 neous paste; dilute to about 10 cc. with water, and add a slight excess of annnonia; 

 pour into a glass tube, make volume to 50 or 100 cc. with distilled water, ami deter- 

 mine nitrates by the ordinary colorimetric method. The silver solution is prepared 

 by heating pulverized silver sulphate with a little water and adding ammonia little 

 by little. Even small amounts of chlorids are shown to interfere with the accuracy 



'Compt. Rend. Acad. Sci. Paris, 101 (1885), p. 62. 

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